Portal for ArcGIS: Unauthorized Unable to sign in. Try again.

Error Message

When accessing the Portal for ArcGIS home page, the following error is returned:

Error:
Unauthorized Unable to sign in. Try again.

When accessing the Portal Administrator Directory, the following error is returned:

Error:   
Site Root -/

 Version: 10.x.x

Site is inaccessible. Contact your Portal administrator

Cause

The issue is caused by the disk location for "arcgisportal\content" running out of space after publishing large datasets, which fills up the disk space. The portal logs indicate the "disk running out of space" warning.

Solution or Workaround

Add or free up disk space on the drive where the "arcgisportal" and "content" directories are stored, then restart the Portal for ArcGIS service. Refer to Portal for ArcGIS: Stop and start the portal for more information.